A groundbreaking international study has uncovered the ancient roots of one of the world’s most important crops – and it all started with an extraordinary chance natural interbreeding event between two wild plants.
Published in the journal Cell, new research led by genomics experts at the Chinese Academy of Agricultural Sciences – with input from taxonomy and evolutionary biology experts at the Natural History Museum – reveals that modern-day potatoes owe their existence to an ancient hybridisation event between the ancestors of the tomato and a potato-like plant called Etuberosum that occurred nine million years ago.
The discovery uncovers a missing piece of the potato’s evolutionary history and solves the mystery of where the world’s third most important staple crop comes from. The answers gleaned from this study means that scientists can turn the potato into a seed crop, with much faster breeding efficiency and a better resistance to disease and climate change.
Lead author, Zhiyang Zhang, of the Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, said: “Wild potatoes are very difficult to sample, so this dataset represents the most comprehensive collection of wild potato genomic data ever analysed.”
Dr Sandy Knapp, Botany researcher at the Natural History Museum and co-author, said: “Science never stops – it keeps asking the next interesting question. The group behind this study came together to see how we can use insights from evolution to speed up and improve breeding of cultivated and domesticated potatoes globally.
“By combining genomic excellence with an understanding of the 107 species of wild potatoes and their distribution, which comes from specimens held in collections like those at the Museum, the team have been able to uncover the very functional underpinning of the heightened diversification of the potato plant lineage – which is quite extraordinary.”
The team analysed 450 potato genomes (including many domestic varieties) and 56 wild relatives to solve the mystery of why modern potato plants look very similar to the wild species of the Etuberosum group (despite the latter not carrying the structure we eat – the tubers) but are evolutionarily-speaking more closely related to tomatoes in some parts of their genomes. The analysis confirmed that the potato carries a balanced genetic legacy from its two ancestors, with key genes inherited from each that together made tuber formation possible.
One gene – SP6A, a signal for tuberisation – came from the tomato side of the family. But it was only when paired with IT1 – a gene regulating underground stem growth from Etuberosum – that the potato was able to evolve the thick, starchy underground storage organ we know today.
This evolutionary leap occurred as the Andes mountains were rapidly rising in a period of major environmental change caused by the Atlantic plate pushing beneath the South American plate. Phylogenetic analysis of today’s members of the two ‘parent plant’ lineages show how they each occupy distinct environmental niches: tomatoes (dry and hot) and Etuberosum (temperate).
The development of tubers (which would become potatoes) by the ancestor of the potato plant gave it a survival advantage in the dry, cold climates of the new high-altitude habitats of the Andes. The underground organs allowed it to reproduce without seeds or pollination (asexually) and spread into a variety of new ecosystems.
Sanwen Huang, co-author of the study, and professor at the Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, China, says: “Evolving a tuber gave potatoes a huge advantage. It fuelled an explosion of species diversity and helped potatoes thrive in some of the most challenging environments on Earth.”
Dr Tiina Särkinen, a nightshade expert at the Royal Botanic Garden Edinburgh and co-author, said: “These results make us look at our humble potato in a very different light: potato and all its wild relatives came to exist thanks to a chance encounter of two very different individuals. That’s actually quite romantic. The origin of many of our species isn’t a simple story, and it’s very exciting that we can now discover these tangled, complex origins thanks to the wealth of genomic data.”
As climate and biodiversity challenges mount, scientists are already asking the next interesting question: how can they use this crop’s evolutionary story to inspire future innovations? Professor Huang and his team at the Chinese Academy of Agricultural Sciences are experimenting with reintroducing key tomato genes into potatoes in a bid to create a new potato reproduced by seeds, enabling fast-iterative breeding of more resilient, productive crops for today’s changing conditions.
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